<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8" />
	<title>nav</title>
	<style>
		*{
			margin: 0;
			padding: 0;
		}
		body{
			background-color: #eee;
			width: auto;
		}
		.contenter{
			width: 100%;
		}
		.nav{
			margin: 0 auto;
			width: 100%;
			text-align: center;
			/*width: 1190px;*/
			height: 70px;
			line-height: 70px;
			background-color: darkslateblue;
		}
		
		.nav_list{
			margin: 0 auto;
			width: 100%;
			display: flex;
		}
		.nav_list .nav_item{
			list-style: none;
			width: 150px;
			float: left;
			cursor: pointer;
			flex: 1;
			color: #fff;
		}
		.item_down{
			height: 0px;
			list-style: none;
			overflow: hidden;
			transition: height 1s;
			-webkit-transition: height 1s;
			-moz-transition: height 1s;
		}
		
		.nav_list:hover .item_down{
			height: 280px;
		}
		
		.nav_item2:hover{
			opacity: .8;
		}
		dt{
			height: 70px;
		}
		
		dd{
			height: 70px;
			background-color: blueviolet;
		}
		
		.footer{
			width: 100%;
			margin: 0 auto;
			clear: both;
			/*top: 0;*/
			background-color: #EEEEEE;
			text-align: center;
		}
	</style>
</head>
<body>
	<div class="contenter">
		<div class="nav">
			<ul class="nav_list">
				<li class="nav_item nav_item1">
					<dt></dt>
					<dl class="item_down">
						<dd></dd>
						<dd></dd>
						<dd></dd>
						<dd></dd>
					</dl>
				</li>
				<li class="nav_item nav_item2">
					<dt>导航2</dt>
					<dl class="item_down">
						<dd>导航2-1</dd>
						<dd>导航2-2</dd>
						<dd>导航2-3</dd>
						<dd>导航2-4</dd>
					</dl>
				</li>
				<li class="nav_item nav_item2">
					<dt>导航3</dt>
					<dl class="item_down">
						<dd>导航3-1</dd>
						<dd>导航3-2</dd>
						<dd>导航3-3</dd>
						<dd>导航3-4</dd>
					</dl></li>
				<li class="nav_item nav_item2">
					<dt>导航4</dt>
					<dl class="item_down">
						<dd>导航4-1</dd>
						<dd>导航4-2</dd>
						<dd>导航4-3</dd>
						<dd>导航4-4</dd>
					</dl>
				</li>
				<li class="nav_item nav_item2">
					<dt>导航5</dt>
					<dl class="item_down">
						<dd>导航5-1</dd>
						<dd>导航5-2</dd>
						<dd>导航5-3</dd>
						<dd>导航5-4</dd>
					</dl>
				</li>
			</ul>
			<div class="footer">
				随便一段文字
			</div>
		</div>
	</div>
	
</body>
</html>